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Interfering Substance
Magnetite (black iron oxide)
or Ferrites
Rust
Sample Collection, Storage and Preservation
Labware
Cleaning the Pour-Thru Cell
Accuracy Check
IronTot_None_Other_FVR_Eng_Ody.fm
(continued)
1. Fill a 50-mL graduated cylinder with 50 mL of sample.
2. Transfer the sample into a clean glass 125-mL Erlenmeyer flask.
3. Add 1.0-mL of FerroZine Iron Reagent Solution Cat. No. 2301-53) and swirl to mix.
4. Place the flask on a hot plate or over a flame and bring to a boil.
5. Continue boiling gently for 20 to 30 minutes.
Note: Do not allow to boil dry.
6. Return the boiled sample to the graduated cylinder. Rinse the Erlenmeyer flask with small
amounts of deionized water and empty into the graduated cylinder.
Note: A purple color will develop if iron is present.
7. Return the sample volume to the 50-mL mark with deionized water.
8. Pour the solution into a 125-mL Erlenmeyer flask and swirl to mix.
Proceed with steps 5–9.
Boil the sample, with the FerroZine
Cool to 24 °C (75 °F) before proceeding with step 8. Return the sample volume to 25 mL with
deionized water.
Collect samples in acid-washed glass or plastic bottles. To preserve samples,
adjust the sample pH to 2 or less with Nitric Acid (Cat. No. 152-49) (about 2 mL
per liter). Samples preserved in this manner can be stored up to six months at
room temperature. Before testing, adjust the pH of the sample to 3–5 with NaOH
ACS (Cat. No. 2450-26); see 3.1.3 Correcting for Volume Additions
Note: Do not exceed pH 5 as iron may precipitate.
If only dissolved iron is to be reported, filter sample immediately after collection
and before addition of nitric acid.
All containers used in this test must be cleaned thoroughly to remove any
traces of iron. Rinse labware and the Pour-Thru Cell with a 1:1 HCl solution
(Cat. No. 884-49) or with a 1:25 dilution of FerroZine
times with deionized water.
Keep flasks tightly closed when not in use. Dedicate these containers for iron
analysis only. If containers are rinsed and capped after each use, only occasional
treatment with HCl or FerroZine
The Pour-Thru Cell may accumulate a buildup of colored products, especially
if the reacted solutions are allowed to stand in the cell for long periods after
measurement. Remove the color by rinsing with a 1:5 dilution of Ammonium
Hydroxide (Cat. No. 106-49), followed by several rinses with deionized water.
Cover the Pour-Thru Cell when it is not in use.
Standard Additions Method (Sample Spike)
1. Snap the neck off an Iron Voluette
Interference Levels
®
Iron Reagent from step 7, for 1 minute in a boiling water bath.
®
®
is necessary.
®
Ampule Standard, 25-mg/L Fe.
Iron
Reagent. Rinse several
Iron
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